PNEUMONIA, VIRAL

PNEUMONIA, VIRAL - Kathleen Doyle, MD
BASICS
DESCRIPTION
• Inflammatory disease of the lungs; affects pulmonary system.
• Most viral pneumonia results from exposure of a susceptible nonimmune person to infection in the form of aerosolized secretions.
ALERT
Geriatric Considerations
Greatest rates of morbidity and mortality
Pediatric Considerations
Adenoviral infections in children are serious. More serious respiratory virus infections are almost always seen in infants and in immunocompromised patients.
Pregnancy Considerations
Pregnant patients should avoid contact with anyone who has a viral infection. Consider vaccination if patient will be >3 months pregnant during the influenza season.
GENERAL PREVENTION
• Influenza A and B vaccine: Use in patients with chronic cardiovascular lung disease, residents of long-term care facilities, medical personnel with extensive contact with high-risk patients, people >50 years of age or those with chronic diseases, immunosuppressed patients (including all those with HIV), health care workers, and people in frequent contact with any high-risk person.
• For those patients who are unable to receive influenza vaccine (e.g., with egg allergy or other) and are at high risk because of age, comorbid illness, or other risk factor, amantadine, rimantadine, or oseltamivir can be given throughout the infectious season if tolerated.
• For those who did not receive the vaccine and have been exposed to influenza, or in geographic areas where an influenza A outbreak has been documented, amantadine, rimantadine, or oseltamivir may also be taken for 2 weeks until vaccination has produced immunity.
• Health care workers who are pregnant must take proper precautions to avoid infectious patients.
• Measles vaccine
• Varicella vaccine
EPIDEMIOLOGY
• Predominant age: Children
• Predominant sex: Male = Female
Prevalence
• Prevalence is unknown, and varies with seasonal outbreaks, but disease is more common during winter months.
• ~90% of all cases of childhood pneumonia have viral cause.
RISK FACTORS
• Immunocompromised state
• Living in close quarters
• Seasonal: Epidemic upper respiratory illness
• Elderly patients
• Cardiac disease
• Chronic pulmonary disease
• Recent upper respiratory infection
• Travel to endemic area (Hantavirus and severe acute respiratory virus)
• Nonvaccinated person
Genetics
No known genetic pattern has been recognized.
ETIOLOGY
• Influenza A, B, and C
• Parainfluenza 1, 2, 3, and 4
• Respiratory syncytial virus (especially in young children)
• Adenovirus
• Cytomegalovirus, particularly in immunocompromised patients
• Varicella (chickenpox)
• Herpes simplex
• Enterovirus
• Coronavirus
• Rubeola (measles)
• Epstein-Barr virus
• Hantavirus
• Human metapneumovirus
• Avian influenza A (H5N1)
• Mixed infection with bacterial pathogens common
• Between 4% and 39% of diagnosed pneumonia in adults has been ascribed to viral cause in different published series.
ASSOCIATED CONDITIONS
• Bacterial forms of pneumonia
• Fungal infection and Pneumocystis jerovici pneumonia/pneumocystic pneumonia in immunocompromised patients


DIAGNOSIS
SIGNS AND SYMPTOMS
• Fever
• Chills
• Cough (with or without purulent sputum production)
• Dyspnea
• Pulmonary rales and rhonchi
• Altered breath sounds
• Pleurisy
• Friction rub
• Headache
• Myalgias
• Malaise
• Gastrointestinal symptoms
History
Avian flu is currently not a risk for persons in the US, but is a risk for those with poultry (chicken, duck, and turkey) contact in Asia, Europe, and the UK.
TESTS
Lab
• Sputum Gram stain and culture to identify bacterial copathogens if present
• Appropriate direct fluorescent antibody or enzyme immunoassay from throat nasopharyngeal washings (children) or swab (adults), tracheal aspirate, or bronchoalveolar lavage specimens (herpes simplex virus, varicella-zoster virus, influenza viruses A and B, respiratory syncytial virus, adenovirus)
• Viral culture
• Cytopathology (cytomegalovirus, herpes simplex virus, measles virus)
• Normal or near normal granulocyte count, occasionally leukopenic with increased lymphocyte percentage
• Hypoxemia with severe disease
• Hemoconcentration (hantavirus)
• Serology (4-fold rise in acute compared with convalescent titers)
• Polymerase chain reaction detection if modality available
• Disorders that may alter lab results: Coronavirus antibody or reverse-transcriptase polymerase chain reaction if severe acute respiratory virus infection is suspected
Imaging
Chest radiograph: Interstitial or alveolar infiltrates, peribronchial thickening, pleural effusion
Diagnostic Procedures/Surgery
• Nasopharyngeal throat swab
• Bronchoscopy with bronchoalveolar lavage
• Serologic testing for hantavirus; enzyme immunoassay if available from health departments
Pathological Findings
• Heavy lungs
• Enlarged regional lymph nodes
• Cytoplasmic inclusion bodies (cytomegalovirus [CMV])
• Intranuclear inclusion bodies (adenovirus, CMV, herpesvirus, varicellovirus)
• Intense inflammatory reaction with mononuclear cells
• Multinucleated giant cells (parainfluenza virus, measles virus, herpes simplex virus, varicellovirus)
DIFFERENTIAL DIAGNOSIS
• Bacterial pneumonia (especially atypical etiologies: Chlamydophilia pneumoniae and C. psittaci, Mycoplasma pneumoniae, Legionella pneumophila)
• Pulmonary edema
• Pneumocystis pneumonia/Pneumocystis jiroveci pneumonia
• Aspiration pneumonia
• Hypersensitivity pneumonitis
• Bronchiolitis obliterans with organizing pneumonia
• Pulmonary embolus/infarction
• Cystic fibrosis (in infants)
• Severe acute respiratory syndrome or severe acute respiratory syndrome-associated Coronavirus
TREATMENT
Outpatient for most cases. Inpatient for infants 4 months of age or older people, or for any patient with diffuse, severe infection (e.g., hypoxemia, hypercarbia, hypotension or shock, adult respiratory distress syndrome) or significant comorbidity (e.g., CHF, coronary artery disease, chronic obstructive pulmonary disease)
GENERAL MEASURES
• Encourage coughing and deep breathing exercises to clear secretions.
• Careful disposal of secretions/universal precautions
• Hydration
• Respiratory isolation for varicella virus, which is highly contagious (i.e., negative pressure)
Diet
Increase fluids; provide high-calorie, high-protein, soft diet
Activity
Rest
MEDICATION (DRUGS)
First Line
• Oseltamivir (Tamiflu): Influenza virus A and B
- Patients >18: 75 mg PO q12h for 5 days; dosage adjusted to 75 mg PO q24h in cases where creatinine clearance rate is 30 mL/min. (Due to resistance development, this was drug of choice for influenza during the 2005-2006 season).
- Rimantadine (Flumadine), an amantadine analog, is equally effective as amantadine and has fewer adverse effects. Useful for Influenza A. Effective only in 1st 24-48 hours. Preferable to amantadine due to lower side effects.
• Acyclovir (Zovirax): Pulmonary infections involving herpes simplex virus, herpes zoster, or varicella virus
- Adults: 5 mg/kg IV q8h for pneumonia caused by herpes simplex virus and 10 mg/kg IV q8h for pneumonia caused by varicellovirus
- Children: 250 mg/m2 IV q8h
• Ganciclovir (Cytovene): Infection owing to cytomegalovirus or herpes simplex virus
- 5 mg/kg IV q12h
• Ribavirin (Virazole): Respiratory syncytial virus, possibly Hantavirus and influenza B virus (20 mg/mL via continuous aerosol administration for 12-18 hours per day for 3-7 days). Indicated only in severe respiratory syncytial virus infections, given via small-particle aerosol generator
• Zanamivir (Relenza): Influenza virus A and B
- Patients 12: 10 mg (2 inhalations) inhaled PO q12h for 5 days
• Contraindications: Refer the to manufacturer's literature.
• Precautions
- Amantadine should be used cautiously in patients with liver disease, epilepsy, renal disease, eczematoid rash, and those with a history of psychotic illness.
- Ribavirin is teratogenic and should not be administered by pregnant health care personnel; its cost is high and benefits are marginal.
• Significant possible interactions: Refer to the manufacturer's literature.
Second Line
• Amantadine (Symmetrel): Influenza A (not effective for influenza B): Effective only in 1st 24-48 hours
- Patients 10 years: 4-8 mg/kg/d PO in 2 divided doses. Not to exceed 150 mg/d PO.
- Patients aged 10-65 years: 100 mg PO q12h. Adults may be given a loading dose of 200 mg PO initially.
• Patients >65: 100 mg PO once a day
• Antibiotics for superimposed bacterial infections
• Foscarnet (Foscavir) for cytomegalovirus, herpes simplex virus, varicellovirus infections, 60 mg/kg IV q8h
• Immune globulin: IV may increase response in non-AIDS, immunosuppressed patients with cytomegalovirus pneumonia. Dose and dosage regimen are not well established, but 500 mg/kg IV daily for 10 doses may be beneficial.
• Amantadine and rimantadine not effective for avian flu, but oseltamivir and zanamivir probably are.
FOLLOW-UP
PROGNOSIS
Usually favorable prognosis, with illness lasting several days to a week. Postviral fatigue is common. However, death can occur, especially in pediatric or bone marrow transplant patients with adenovirus infections or in older people with influenza.
COMPLICATIONS
• Superimposed bacterial infections such as Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and others
• Respiratory failure requiring mechanical ventilation
• Adult respiratory distress syndrome
• Reye syndrome after influenza in children
PATIENT MONITORING
• Physical examinations
• Chest radiograph
• Oxygenation if illness severe enough for hospitalization
REFERENCES
1. Mandell GL, ed. Principles and Practice of Infectious Diseases, 6th ed. Philadelphia: Churchill Livingstone, 2005.
2. de Roux A, et al. A. Viral community-acquired pneumonia in nonimmunocompromised adults. Chest. 2004;125(4):1343-1351.
3. Fields BN, Knipe DM, Chanock RM, eds. Virology, 2nd ed. New York: Raven, 1990.
4. Gorbach SL, Bartlett JG, Blacklow NR, eds. Infectious Diseases. Philadelphia: WB Saunders, 1998.
ADDITIONAL READING
• www.cdc.gov/flu/pandemic
• www.idsociety.org
MISCELLANEOUS
• See also: Bronchiolitis obliterans; Severe acute respiratory syndrome.
• Information on severe acute respiratory syndrome for clinicians is available at cdc.gov/ncidod/sars/clinicians.htm.